txhaj tshuaj molding txheej txheem cuam tshuam cov yam

Hauv txhaj tshuaj txheej txheem molding ntawm cov yas, thermoplastics, vim lub ntim hloov los ntawm crystallization, muaj zog sab hauv kev nyuaj siab, loj residual kev nyuaj siab khov nyob rau hauv cov yas ib feem, muaj zog molecular orientation thiab lwm yam, thiaj piv nrog thermoset plastics, tus nqi shrinkage yog loj dua. Tus nqi shrinkage yog dav thiab lub directionality yog pom tseeb. Ntxiv thiab, lub shrinkage tom qab molding, annealing lossis vaum kev kho mob feem ntau loj dua li ntawm cov thermosetting plastics.

Thaum cov yas yog molded, cov khoom molten hu rau saum npoo ntawm cov kab noj hniav thiab txheej txheej yog tam sim ntawd txias kom tsim ib lub plhaub uas tsis muaj qhov ntom ntom.. Vim tsis zoo thermal conductivity ntawm cov yas, Sab hauv txheej ntawm cov yas yog maj mam txias los ua cov txheej high-ceev txheej nrog loj shrinkage. Yog li ntawd, phab ntsa thickness, qeeb txias, thiab high-density txheej thickness yuav shrink ntau. Ntxiv thiab, lub xub ntiag los yog tsis muaj inserts thiab layout thiab kom muaj nuj nqis ntawm inserts ncaj qha cuam tshuam rau cov kev taw qhia ntawm cov khoom ntws., density faib thiab shrinkage kuj. Yog li ntawd, cov yam ntxwv ntawm cov khoom yas muaj kev cuam tshuam ntau dua rau kev shrinkage thiab directionality.

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Yam xws li daim ntawv, qhov loj, thiab kev faib tawm ntawm cov khoom noj nkag ncaj qha cuam tshuam rau kev coj ntawm cov khoom ntws, kev faib tawm ceev, siab tswj thiab shrinking nyhuv thiab molding lub sij hawm. Direct feed ports thiab feed ports with large cross-sections (tshwj xeeb tshaj yog thicker cross-section) muaj tsawg shrinkage tab sis ntau dua directivity, thiab luv pub chaw nres nkoj nrog luv luv thiab ntev muaj tsawg directivity. Cov uas nyob ze rau qhov pub nkag los yog sib npaug rau cov kev taw qhia ntawm cov khoom ntws yuav ntsws ntau dua.

Moulding tej yam kev mob: pwm kub, qeeb txias ntawm cov khoom molten, siab ceev thiab loj shrinkage, tshwj xeeb tshaj yog rau cov ntaub ntawv crystalline, vim siab crystallinity thiab loj ntim hloov, yog li qhov shrinkage ntau dua. Cov pwm kub faib kuj tseem muaj feem xyuam rau cov cua txias sab hauv thiab sab nraud thiab qhov ntom ntom ntom ntom ntawm cov yas, uas ncaj qha cuam tshuam qhov loj thiab kev coj ntawm shrinkage ntawm txhua feem. Ntxiv thiab, tuav lub siab thiab lub sij hawm kuj muaj kev cuam tshuam ntau dua rau kev cog lus, thiab qhov contraction me me tab sis lub directionality loj dua thaum lub siab yog siab thiab lub sij hawm ntev.

Kev txhaj tshuaj siab yog siab, cov yaj viscosity sib txawv me me, lub interlayer shear stress yog me me, thiab elastic rebound tom qab demolding yog loj, yog li lub shrinkage kuj yuav raug txo los ntawm tus nqi tsim nyog. Cov khoom kub yog siab, lub shrinkage yog loj, tab sis lub directionality yog me me. Yog li ntawd, kho cov pwm kub, siab, txhaj tshuaj ceev thiab lub sij hawm txias thaum lub sij hawm molding kuj tsim nyog hloov lub shrinkage ntawm yas ib feem.

Thaum tsim pwm, raws li qhov shrinkage ntau yam ntawm ntau yam yas, phab ntsa thickness thiab cov duab ntawm cov yas ib feem, qhov loj thiab kev faib tawm ntawm daim ntawv inlet, tus nqi shrinkage ntawm txhua feem ntawm cov yas yog txiav txim siab raws li kev paub dhau los, thiab ces cov kab noj hniav loj yog xam. Rau high-precision yas qhov chaw thiab thaum nws nyuaj rau tuav tus nqi shrinkage, cov txheej txheem hauv qab no feem ntau yuav tsum tau siv los tsim pwm:

① Kev sim pwm txiav txim siab daim ntawv, qhov loj thiab molding tej yam kev mob ntawm lub rooj vag system.

② Cov khoom yas uas yuav tsum tau ua tom qab yuav tsum tau ua tiav los txiav txim siab qhov hloov pauv loj (qhov ntsuas yuav tsum yog 24 teev tom qab demolding.

③ Kho cov pwm raws li qhov tseeb shrinkage.

④ Rov sim cov pwm thiab tsim nyog hloov cov txheej txheem rau me ntsis hloov tus nqi shrinkage kom tau raws li qhov yuav tsum tau muaj ntawm cov khoom yas.

Lub fluidity ntawm thermoplastics feem ntau tuaj yeem txheeb xyuas los ntawm ntau qhov ntsuas xws li qhov hnyav molecular, yaj index, Archimedes kauv flow length, pom meej viscosity thiab flow ratio (txheej txheem ntev / yas ntu phab ntsa thickness).

Me me molecular hnyav, dav molecular hnyav tis, pluag molecular qauv tsis tu ncua, siab melt index, ntev spiral flow length, tsawg pom tseeb viscosity, siab flow ratio, zoo fluidity, plastics nrog tib lub npe khoom yuav tsum xyuas lawv cov lus qhia los txiav txim seb lawv cov fluidity puas siv tau rau kev txhaj tshuaj molding. Raws li kev tsim pwm tsim, cov fluidity ntawm cov khoom siv feem ntau tuaj yeem muab faib ua peb pawg:

① Zoo fluidity PA, ON, PS, PP, CA, poly(4) methylpenene:

②Polystyrene series resin nrog nruab nrab fluidity (xws li ABS, AS), PMMA, POM, polyphenylene ether;

③ Fluidity tsis zoo: PC, tawv PVC, polyphenylene ether, polysulfone, polyarylsulfone, fluoroplastics.

Lub fluidity ntawm ntau yam yas kuj hloov vim muaj ntau yam molding yam. Lub ntsiab cuam tshuam muaj xws li hauv qab no:

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① Cov khoom siv kub siab ua kom muaj dej ntau ntxiv, tab sis txawv plastics muaj lawv tus kheej sib txawv, xws li PS (tshwj xeeb tshaj yog cov uas muaj kev cuam tshuam siab thiab siab dua MFR tus nqi), PP, PA, PMMA, hloov kho polystyrene (xws li ABS, AS) Lub fluidity ntawm, PC, CA thiab lwm yam yas sib txawv nrog qhov kub thiab txias. Rau PE thiab POM, qhov kub nce lossis txo qis tsis zoo cuam tshuam rau lawv cov fluidity. Yog li ntawd, tus qub yuav tsum tau kho qhov kub thiab txias thaum lub sij hawm molding tswj fluidity.

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② Raws li lub siab ntawm kev txhaj tshuaj molding nce, cov khoom molten yuav raug ntau dua shear thiab fluidity, tshwj xeeb tshaj yog PE thiab POM rhiab heev, yog li qhov kev txhaj tshuaj siab yuav tsum tau kho kom tswj tau qhov dej thaum lub sij hawm molding.

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③ Daim ntawv, qhov loj, layout, cua txias system tsim, flow resistance ntawm cov khoom molten (xws li qhov chaw tiav, lub thickness ntawm lub channel seem, cov duab ntawm kab noj hniav, lub tso pa system) thiab lwm yam ntawm cov pwm qauv casting system ncaj qha cuam tshuam cov khoom molten hauv kab noj hniav Qhov tseeb fluidity hauv, yog hais tias cov khoom molten yog txhawb kom txo qhov kub thiab nce lub fluidity kuj, fluidity yuav txo.

Thaum tsim pwm, tus qauv tsim nyog yuav tsum tau xaiv raws li qhov fluidity ntawm cov yas siv. Thaum molding, cov khoom kub, pwm kub, txhaj tshuaj siab, Kev txhaj tshuaj nrawm thiab lwm yam tseem tuaj yeem tswj tau kom tsim nyog kho qhov ntim kom tau raws li cov kev xav tau molding.

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Crystalline thermoplastics tuaj yeem muab faib ua crystalline plastics thiab non-crystalline (kuj hu ua amorphous) plastics raws li lawv tsis muaj crystallization thaum condensation. Qhov tshwm sim hu ua crystallization yog hais txog qhov tseeb tias thaum cov yas hloov los ntawm lub xeev molten mus rau lub xeev condensation., cov molecules txav ntawm nws tus kheej thiab yog kiag li nyob rau hauv ib tug tsis meej lub xeev. Cov molecules nres txav mus los, nias ib qho chaw ruaj me ntsis, thiab muaj kev nyiam ua kom cov molecular kev npaj ua qauv tsis tu ncua. Qhov no tshwm sim.

Cov txheej txheem zoo li kev txiav txim siab ntawm ob hom yas no tuaj yeem txiav txim siab los ntawm qhov pom tseeb ntawm cov yas tuab tuab.. Feem ntau, crystalline cov ntaub ntawv yog opaque los yog translucent (zoo li POM, lwm yam.), thiab cov ntaub ntawv amorphous yog pob tshab (xws li PMMA, lwm yam.). Tab sis muaj kev zam. Piv txwv, poly(4) methylpentene yog cov yas crystalline tab sis muaj pob tshab siab, thiab ABS yog cov khoom siv amorphous tab sis tsis pob tshab.

Thaum tsim pwm thiab xaiv cov tshuab txhaj tshuaj molding, ua tib zoo saib xyuas cov cai hauv qab no thiab kev ceev faj rau cov khoom siv crystalline:

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① Yuav tsum muaj cua sov ntau rau cov khoom siv kub kom nce mus rau molding kub, thiab cov khoom siv uas muaj peev xwm plasticizing loj yog xav tau. Rau

②Nws tso cua sov ntau thaum lub sijhawm txias rov qab thiab yuav tsum tau txias txaus.

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③Qhov sib txawv ntawm qhov sib txawv ntawm lub xeev molten thiab lub xeev cov khoom yog loj, molding shrinkage yog loj, thiab shrinkage thiab pores yog nquag tshwm sim.

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④ Ceev ceev, tsawg crystallinity, me me shrinkage thiab siab transparency. Lub crystallinity muaj feem xyuam rau cov phab ntsa thickness ntawm cov yas, thiab phab ntsa thickness yog qeeb kom txias, lub crystallinity yog siab, lub shrinkage yog loj, thiab lub cev muaj zog yog qhov zoo. Yog li ntawd, pwm kub ntawm cov khoom siv crystalline yuav tsum tau tswj raws li qhov xav tau.

⑤ Qhov tseem ceeb anisotropy thiab kev ntxhov siab loj. Cov molecules uas tsis crystallized tom qab demolding muaj ib tug nyiam mus ntxiv crystallize, nyob rau hauv lub zog tsis txaus ntseeg, thiab nws yooj yim rau deformation thiab warpage. ⑥ Lub crystallization kub ntau yog nqaim, thiab cov khoom siv tsis tau yaj yog nquag txhaj rau hauv pwm lossis thaiv qhov chaw nres nkoj pub.

Thaum tshav kub kub rhiab heev yog hais txog qhov nyiam ntawm qee yam plastics kom nkag siab ntau dua rau cov cua sov. Thaum rhuab ntawm qhov kub siab ntev ntev los yog qhov chaw nres nkoj pub me me dhau, thaum cov nyhuv shearing loj, cov khoom kub nce thiab nyiam ntawm discoloration, degradation, thiab decomposition tshwm sim. Yas yog hu ua cov yas uas muaj cua sov.

Xws li tawv PVC, polyvinylidene chloride, vinyl acetate copolymer, POM, polychlorotrifluoroethylene, lwm yam. Thaum tshav kub kub-rhiab plastics tsim monomers, cov pa, solids thiab lwm yam by-products thaum decomposition. tshwj xeeb, Qee qhov decomposition gases muaj irritating, corrosive los yog tshuaj lom rau tib neeg lub cev, khoom siv, thiab pwm. Yog li ntawd, xim yuav tsum tau them rau pwm tsim, txhaj tshuaj molding tshuab xaiv thiab molding. Cov ntsia hlau txhaj tshuaj molding tshuab yuav tsum tau siv. Cov seem ntawm cov txheej txheem pouring yuav tsum loj. Cov pwm thiab lub thoob yuav tsum yog chrome-plated. Yuav tsum tsis muaj kaum stagnation. Cov molding kub yuav tsum tau tswj nruj heev. Stabilizer, tsis muaj zog nws qhov kev ua haujlwm kub-rhiab heev.

Ib txhia yas (xws li PC) txawm muaj me me dej, tab sis lawv yuav decompose nyob rau hauv qhov kub thiab txias. Cov cuab yeej no hu ua yooj yim hydrolysis, uas yuav tsum tau rhuab thiab qhuav ua ntej.

Yog tias koj muaj lus nug txogtxhaj tshuaj molding txheej txheem,plz xav tias dawb nug peb,peb yuav muab kev pabcuam zoo tshaj rau koj!

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